A new route to methyl (R,E)-(-)-tetradeca-2,4,5-trienoate (pheromone of Acanthoscelides obtectus) utilizing a palladium-catalyzed asymmetric allene formation reaction

Article abstract of DOI:10.1021/jo050684z

A formal total synthesis of the sex attractant of male dried bean beetle, methyl (R,E)-(-)-tetradeca-2,4,5-trienoate, was achieved by a new efficient route utilizing the Pd-catalyzed asymmetric allene synthesis reaction. It was found that the atropisomeric biaryl bisphosphine (R)-segphos showed better enantioselectivity than (R)-binap in the Pd-catalyzed reaction for preparing alkyl-substituted axially chiral allenes.

Full text of DOI:10.1021/jo050684z

A New Route to Methyl
SCHEME 1
(
R,E)-(-)-Tetradeca-2,4,5-trienoate
(
Pheromone of Acanthoscelides obtectus)
Utilizing a Palladium-Catalyzed
Asymmetric Allene Formation Reaction
Masamichi Ogasawara,*,† Takashi Nagano, and
‡
Tamio Hayashi*,‡
Catalysis Research Center and Graduate School of
Pharmaceutical Sciences, Hokkaido University,
Kita-ku, Sapporo 001-0021, Japan, and Department of
Chemistry, Graduate School of Science, Kyoto University,
Sakyo, Kyoto 606-8502, Japan
(R,E)-tetradeca-2,4,5-trienoate ((R)-1), which is a natu-
5
rally occurring allene and a sex pheromone of male dried
6-8
bean beetle,
by utilizing the asymmetric allene syn-
thesis protocol. Among the known synthetic methods of
the nonracemic pheromone,8 our method is the first
example of inducing the allenic axial chirality in (R)-1
by a catalytic asymmetric reaction. It has been known
that the pheromone extracted from the insect is optically
active but not enantiomerically pure with ca. 79-81%
ogasawar@cat.hokudai.ac.jp; thayashi@kuchem.kyoto-u.ac.jp
Received April 7, 2005
6
a,8b,9
ee.
Our asymmetric reaction gives certain axially
chiral allenes with fairly high enantiomeric excess;
however, the enantioselectivity still has room for further
improvement. Indeed, while investigating its application
to asymmetric synthesis of the pheromone, we had
encountered the necessity to enhance the enantioselec-
(
4) For transition-metal-catalyzed kinetic resolutions of racemic
chiral allenes, see: (a) Noguchi, Y.; Takiyama, H.; Katsuki, T. Synlett
A formal total synthesis of the sex attractant of male dried
bean beetle, methyl (R,E)-(-)-tetradeca-2,4,5-trienoate, was
achieved by a new efficient route utilizing the Pd-cata-
lyzed asymmetric allene synthesis reaction. It was found
that the atropisomeric biaryl bisphosphine (R)-segphos
showed better enantioselectivity than (R)-binap in the
Pd-catalyzed reaction for preparing alkyl-substituted axially
chiral allenes.
1
998, 543. (b) Sweeney, Z. K.; Salsman, J. L.; Andersen, R. A.;
Bergman, R. G. Angew. Chem., Int. Ed. 2000, 39, 2339. For transition-
metal-catalyzed dynamic kinetic resolutions of racemic chiral allenes,
see: (c) Imada, K.; Ueno, K.; Kutsuwa, K.; Murahashi, S.-I. Chem. Lett.
2
002, 140.
(
5) (a) Robinson, C. H.; Covey, D. F. In The Chemistry of Ketenes,
Allenes, and Related Compounds; Patai, S., Ed.; Wiley: Chichester,
1980; p 451. (b) Landor, S. R. In The Chemistry of the Allenes; Landor,
S. R., Ed.; Academic Press: London, 1982; p 679. (c) Krause, N.;
Hoffmann-R o¨ der, A. In Modern Allene Chemistry; Krause, N., Hashmi,
A. S. K., Eds.; Wiley-VCH: Weinheim, 2004; p 997. (d) Hoffmann-
R o¨ der, A.; Krause, N. Angew. Chem., Int. Ed. 2004, 43, 1196.
(6) (a) Horler, D. F. J. Chem. Soc. (C) 1970, 859. (b) Halstead, D. G.
H. J. Stored Prod. Res. 1973, 9, 109.
Recently, we have developed a novel palladium-
catalyzed reaction of preparing functionalized allenes
(
7) For preparation of the pheromone (()-1 in racemic form, see:
1
from 1-hydrocarbyl-2-bromo-1,3-butadienes, which were
(
a) Landor, P. D.; Landor, S. R.; Mukasa, S. J. Chem. Soc. D, Chem.
easily derived from the corresponding aldehydes in high-
Commun. 1971, 1638. (b) Descoins, C.; Henrick, C. A.; Siddall, J. B.
Tetrahedron Lett. 1972, 13, 3777. (c) Baudouy, R.; Gor e´ , J. Synthesis
1
a
yields. The Pd-catalyzed reaction has been extended
into an asymmetric counterpart using a Pd/(R)-binap
catalyst, and enantiomerically enriched axially chiral
1
1
974, 573. (d) Michelot, D.; Linstrumelle, G. Tetrahedron Lett. 1976,
7, 275. (e) Kocienski, P. J.; Cernigliaro, G.; Feldstein, G. J. Org. Chem.
1977, 42, 353. (f) Doussal, B. L.; Coq, A. L.; Gorgues, A.; Meyer, A.
Tetrahedron 1983, 39, 2185. (g) Ledoussal, B.; Gorgues, A.; Coq, A. L.
Tetrahedron Lett. 1985, 26, 51. (h) Lang, R. W.; Kohl-Mines, E.;
Hansen, H. J. Helv. Chim. Acta 1985, 68, 2249. (i) Bloch, R.; Hassan-
Gonzales, D. Tetrahedron 1986, 42, 4975. (j) Krause, N.; Gerold, A.
Angew. Chem., Int. Ed. Engl. 1997, 36, 186.
2
allenes were obtained with up to 89% ee (Scheme 1). The
reaction is a rare example of transition-metal-catalyzed
asymmetric synthesis of axially chiral allenes.3 In
this paper, we report a formal total synthesis of methyl
,4
(
8) For preparation of the pheromone (R)-(-)-1 in optically active
form; see: (a) Pirkle, W. H.; Boeder, C. W. J. Org. Chem. 1978, 43,
2091. (b) Mori, K.; Nukada, T.; Ebata, T. Tetrahedron 1981, 37, 1343.
(c) Oehlschlager, A. C.; Czyzewska, E. Tetrahedron Lett. 1983, 24, 5587.
(d) Franck-Neumann, M.; Martina, D.; Neff, D. Tetrahedron: Asym-
metry 1998, 9, 697. (e) Satoh, T.; Hanaki, N.; Kuramochi, Y.; Inoue,
Y.; Hosoya, K.; Sakai, K. Tetrahedon 2002, 58, 2533.
†
Hokkaido University.
Kyoto University.
‡
(1) (a) Ogasawara, M.; Ikeda, H.; Hayashi, T. Angew. Chem., Int.
Ed. 2000, 39, 1042. (b) Ogasawara, M.; Ikeda, H.; Nagano, T.; Hayashi,
T. Org. Lett. 2001, 3, 2615. (c) Ogasawara, M.; Ge, Y.; Uetake, K.; Fan,
L.; Takahashi, T. J. Org. Chem. 2005, 70, 3871.
(9) The maximum optical rotation value for (R)-(-)-1 reported so
8
b
(
2) (a) Ogasawara, M.; Ikeda, H.; Nagano, T.; Hayashi, T. J. Am.
far is -162 (in hexane) by Mori and co-workers. They evaluated the
enantiopurity of their sample as “not higher than 92%” based on the
optical purity of the starting compound they employed for the synthesis
Chem. Soc. 2001, 123, 2089. (b) Ogasawara, M.; Ueyama, K.; Nagano,
T.; Mizuhata, Y.; Hayashi, T. Org. Lett. 2003, 5, 217.
(
3) (a) de Graaf, W.; Boersma, J.; van Koten, G.; Elsevier: C. J. J.
of the pheromone. However, judging from our data (ee’s and [R]
D
Organomet. Chem. 1989, 378, 115. (b) Matsumoto, Y.; Naito, M.;
Uozumi, Y.; Hayashi, T. J. Chem. Soc., Chem. Commun. 1993, 1468.
values) for (R)-1 as well as for (R)-4 of which ee values were determined
by the chiral HPLC technique, the compounds ((R)-1 and (R)-4)
reported in ref 8 appeared to be nearly enantiomerically pure.
Assuming that the Mori’s sample was enantiomerically pure, the
natural pheromone (R)-1 could be estimated to be 79% ee. On the other
hand, the optical purity of the natural pheromone was calculated to
be 81% by comparison with the sample prepared in this study.
(
1
c) Tillack, A.; Michalik, D.; Koy, C.; Michalik, M. Tetrahedron Lett.
999, 40, 6567. (d) Tillack, A.; Koy, C.; Michalik, D.; Fischer, C. J.
Organomet. Chem. 2000, 603, 116. (e) Han, J. W.; Tokunaga, N.;
Hayashi, T. J. Am. Chem. Soc. 2001, 123, 12915. (f) Hayashi, T.;
Tokunaga, N.; Inoue, K. Org. Lett. 2004, 6, 305.
10.1021/jo050684z CCC: $30.25 © 2005 American Chemical Society
5764
J. Org. Chem. 2005, 70, 5764-5767
Published on Web 06/08/2005

SCHEME 2
(48%). The low chemical yield of 3 could be partly
ascribed to the formation of bisallene species meso- and
dl-6, which were obtained in 44% yield. Because the
alkyl-substituted malonate 3 is more reactive than un-
substituted malonate 5 toward the palladium-catalyzed
reaction, the initially formed 3 was deprotonated and
1
t
reacted with 2 as a nucleophile giving 6. Use of CsO Bu
as a base in place of NaH improved the yield of 3 as well
as the enantioselectivity (entry 2). We have reported
recently that (R)-segphos is superior to (R)-binap in terms
of enantioselectivity in the Pd-catalyzed preparation of
axially chiral (allenylmethyl)silanes, which are closely
related to the present study.2b Thus, application of (R)-
TABLE 1. Pd-Catalyzed Asymmetric Reaction of 2
with 5
1
1
segphos to the present reaction was examined. It was
found that a palladium/(R)-segphos catalyst showed
much higher enantioselectivity and (R)-3 was obtained
in 77% ee, although the 3/6 selectivity was poorer (entry
3
). With 5 equiv of the nucleophile, the formation of 6
was reduced to 18%, but the enantiopurity of (R)-3 was
lowered to 67% ee (entry 4). A reaction using 5 equiv of
5
recovery or
t
in the presence of a stoichiometric amount of CsO Bu
a
equiv to 2
base
1.2 1.2
CsO Bu 1.2 1.2
yield (%)
ee of 3b
(with respect to 2) gave (R)-3 of 77% ee in 71% yield
entry 5). Under these conditions, the formation of 6 was
entry
P-P*
base
NaH
5
2
3
6
(%)
(
1
2
3
4
5
(R)-binap
(R)-binap
48 44
61 24
47 36
83 18
39
49
77
67
nearly suppressed. The starting substrate 2 was recov-
ered in 26% yield, and thus the yield of (R)-3 based on
the consumed 2 was calculated to be as high as 96%.
After these examinations, it was decided that (R)-3
obtained under the optimized conditions of entry 5 (77%
ee) was suitable for the following steps.
t
t
(R)-segphos CsO Bu 1.2 1.2
t
(R)-segphos CsO Bu 5.0 5.0
(R)-segphos CsO Bu 5.0 1.0 26 71
t
c
2
77
a
Isolated yield by silica gel chromatography. b Determined by
HPLC analysis with chiral stationary phase column (Daicel
i
c
Application of (R)-Segphos to the Pd-Catalyzed
Allene Preparation. The advantages of (R)-segphos
over (R)-binap are recognized in the reaction in Table 1
as well as in the preparation of axially chiral (allenyl-
Chiralcel OD-H, hexane/ PrOH ) 500/1). [R]D ) -45.8 (c ) 1.08,
hexane).
tivity of the reaction for obtaining (R)-1 of reasonable
optical purity. It was found that the problem could be
solved by the use of (R)-segphos as a chiral supporting
ligand in place of (R)-binap.2b In this paper, the scope
and limitation of the Pd/(R)-segphos catalyst in the allene
preparation will be described as well.
2b
methyl)silanes that was reported previously. With these
observations, the scope and limitation of the use of (R)-
segphos were explored for the allene preparation reac-
10
tions with other 2-bromo-1,3-diene substrates using the
t
combination of HC(NHAc)(COOEt)
2
and CsO Bu as a
nucleophile, of which applications to the asymmetric
Strategy for Asymmetric Synthesis of the Phero-
mone. Our synthetic plan for methyl (R,E)-tetradeca-
2a
allene synthesis were thoroughly studied (Table 2).
Unlike the above-mentioned examples, (R)-segphos showed
lower performance than (R)-binap for the reactions with
a phenyl-substituted diene 7 (entries 1 and 2). The
Pd/(R)-segphos catalyst gave the allene 9 in lower yield
with lower ee. Contrary to these, the superiority of (R)-
segphos was observed for the preparation of allenes from
the alkyl-substituted dienes 8 and 2. The Pd/(R)-segphos
showed better enantioselectivity than the Pd/(R)-binap
2
,4,5-trienoate ((R)-1) is outlined in Scheme 2. Starting
2a
from 3-bromo-1,3-dodecadiene (2), which is easily de-
rived from commercially available nonanal (see the
Supporting Information for details), the axially chiral
4
c
allene (R)-3 would be prepared in an optically active
form by the Pd-catalyzed asymmetric reaction using
dimethyl malonate (5) as a pronucleophile. Removing one
of the two methoxycarbonyl groups in (R)-3 would afford
(
entries 3 vs 4 and 7 vs 8); however, its catalytic activity
(
R)-methyl tetradeca-4,5-dienoate ((R)-4), which had been
was lower at 20 °C and the allenes 10 and 11 were
obtained in 6% and 12% yields, respectively (entries 4
and 8). By running the reactions at higher temperatures
in THF, the low activity of the Pd/(R)-segphos catalyst
was improved (entries 5 and 9). The allene 10 obtained
at 60 °C in THF showed slightly lower ee (89% ee) than
the product from entry 4 (93% ee at 20 °C). Interestingly,
for the reactions of 2 using the Pd/(R)-segphos, the better
7
e,8a-b
demonstrated as the key intermediate to (R)-1.
Catalytic Asymmetric Synthesis of (R)-3. Trans-
formation of the bromodiene 2 into (R)-3 was examined
under various conditions, and the results are summarized
in Table 1. When the asymmetric reaction was carried
out in THF with an equimolar mixture of the pronucleo-
phile 5 and NaH (1.2 equiv to 2) in the presence of the
palladium catalyst (10 mol %) generated from Pd(dba)
2
and (R)-binap (entry 1),2a we encountered two problems:
(11) Whereas use of a bidentate triarylphosphine ligand is essential
1
a
in the Pd-catalyzed allene preparation, axially chiral biaryl phos-
one was the low enantioselectivity of the reaction (39%
ee), and the other was the low chemical yield of (R)-3
2a
phines are rationalized choices as chiral ligands for the present study.
Other axially chiral biaryl phosphines examined so far are (R)-H -binap
and (R)-binap’s with modified PAr groups (Ar ) -C -3,5-Me -4-
8
2
6
H
2
2
OMe and p-tol); however, none of them showed better enantioselectivity
than (R)-segphos for the reaction of 8 with HC(NHAc)(COOEt)
2
(
10) Saito, T.; Yokozawa, T.; Ishizaki, T.; Moroi, T.; Sayo, N.; Miura,
T.; Kumobayashi, H. Adv. Synth. Catal. 2001, 343, 264.
(Ogasawara, M.; Nagano, T.; Hayashi, T. Unpublished results).
J. Org. Chem, Vol. 70, No. 14, 2005 5765

TABLE 2. (R)-Binap vs (R)-Segphos in the Pd-Catalyzed
SCHEME 3
Asymmetric Synthesis of Allenes from Bromodienes
R in
diene
T
yielda
(%)
eeb
(%)
entry
P-P*
solvent (°C)
1c
2
Ph (7)
Ph (7)
(R)-binap
CH2Cl2
20
20
20
20
60
60
20
20
40
75 (9)
89
83
75
93
89
67
54
70
74
(R)-segphos CH2Cl2
60 (9)
c
t
3
Bu (8)
(R)-binap
CH2Cl2
74 (10)
6 (10)
87 (10)
92 (10)
73 (11)
12 (11)
63 (11)
t
4
5
6
Bu (8)
(R)-segphos CH2Cl2
(R)-segphos THF
t
Bu (8)
acidic decarboxylation at 100 °C and a diazomethane
treatment. The overall yield of the process is 60%, and
the product was obtained without appreciable loss of
enantiopurity (76% ee).
t
Bu (8)
(R)-binap
THF
CH2Cl2
c
n
n
n
7
8
9
Oct (2) (R)-binap
Oct (2) (R)-segphos CH2Cl2
Oct (2) (R)-segphos THF
a
Isolated yield by silica gel chromatography. b Determined by
Absolute Configurations of the Allenic Products
from the Pd-Catalyzed Asymmetric Reaction. The
HPLC analysis with chiral stationary phase column (see ref 2a).
Taken from ref 2a.
c
obtained (R)-4 was converted to the pheromone (R)-1
according to the reported method.7
e,8a,b,16
The chiral HPLC
TABLE 3. Decarboxylation of (R)-3 Giving (R)-4
analysis revealed that optical purity of the axially chiral
allenes was retained during the transformation of (R)-4
into (R)-1. Consequently, the asymmetric total synthesis
of the sex pheromone of male dried bean beetle was
completed by the new efficient route in practically the
comparable optical purity as in the natural sample.
yielda
(%)
ee of 4b
(%)
entry
1
conditions
LiI (5.5 equiv), NaCN (1.0 equiv)
in DMF, 120 °C, 6 h
NaCl (0.5 equiv), H2O (3.0 equiv)
in DMSO, 130 °C, 8h
(1) KOH in H2O/MeOH,
82
35
60
54
69
76c
2
3
2
In the previous reports, the absolute configurations
of the axially chiral allenic products were deduced by the
Lowe-Brewster rule.17 Since the relation between the
absolute configuration of the pheromone and its sign of
optical rotation has been known (the (R)-enantiomer
7
0 °C, 30 min
(
2) H2SO4 (cat.) in H2O,
00 °C, 2 days
3) CH2N2 in Et2O
1
(
a
Isolated yield by silica gel chromatography. b Determined by
8a
exhibits levorotatory), we had an opportunity to test the
HPLC analysis with chiral stationary phase column (Daicel
validity of the Lowe-Brewster rule in the Pd-cata-
lyzed asymmetric reaction. As summarized in Scheme
i
c
Chiralcel OD-H, hexane/ PrOH ) 500/1). [R]D ) -47.3 (c ) 1.05,
hexane).
3
, the allenic products 1, 3, and 4 were all levorota-
tory, and thus their absolute configurations were de-
duced to be (R) by the Lowe-Brewster rule. This stereo-
chemical conclusion for the synthetic 1 showed good
agreement with the reported data for the naturally
occurring (R)-(-)-1. During the transformations in Scheme
enantioselectivity of 74% ee was observed at 40 °C in
THF (entry 9) compared to the reaction at 20 °C in
dichloromethane (70% ee, entry 8).
Decarboxylation of (R)-3. Using (R)-3 of 77% ee,
decarboxylation giving (R)-4 was examined (Table 3).12
Direct removal of one of the ester groups in (R)-3 was
achieved by treatment with LiI and NaCN in DMF at
3, the allenic stereochemistry had been retained. Accord-
ingly, it can be concluded that the Lowe-Brewster rule
has drawn the correct absolute configurations for 3 and
1
20 °C (entry 1).13 However, the decarboxylation pro-
4
as well.
ceeded with partial racemization of the allenic axial
In summary, we have developed a novel and efficient
1
4
chirality, and (R)-4, which was obtained in 82% yield,
was found to have 54% ee. A reaction of (R)-3 with NaCl
in aqueous DMSO at 130 °C gave (R)-4 of 69% ee in 35%
method for the preparation of the sex attractant of male
dried bean beetle, methyl (R,E)-tetradeca-2,4,5-trienoate,
utilizing the palladium-catalyzed asymmetric allene
synthesis as the key reaction. The unique axial chirality
in the pheromone was induced by the transition-metal-
catalyzed asymmetric reaction and the pheromone was
obtained in 76% ee, which is practically the comparable
optical purity as in the sample extracted from the natural
source. During this study, the better performances of (R)-
segphos over (R)-binap in the Pd-catalyzed reaction,
especially for the preparation of the alkyl-substituted
axially chiral allenes, were recognized.
1
5
yield (entry 2). The racemization could be practically
suppressed under the conditions of entry 3. That is a
three-step process of methanolic hydrolysis followed by
(
12) For reviews on decarboxylation, see: (a) McMurry, J. Org.
React. 1976, 24, 187. (b) Krapcho, A. P. Synthesis 1982, 805. (c)
Krapcho, A. P. Synthesis 1982, 893.
(
13) Trost, B. M.; Weber, L.; Strege, P. E.; Fullerton, T. J.; Dietsche,
T. J. J. Am. Chem. Soc. 1978, 100, 3416.
14) Thermal racemization of axially chiral allenes was reported and
(
the racemization barriers in 1,3-dialkylallenes were estimated to be
about 46 kcal/mol. However, the reaction temperatures in Table 3 are
relatively low and a mechanism of the racemization at the decarboxy-
lation of (R)-3 is still uncertain. See: (a) Maitland, P.; Mills, W. H. J.
Chem. Soc. 1936, 987. (b) Roth, W. R.; Ruf, G.; Ford, P. W. Chem. Ber.
(16) For preparation of 4, see also: (a) Fujisawa, T.; Iida, S.; Sato,
T. Tetrahedron Lett. 1984, 25, 4007 (in an optically active form). (b)
Tabuchi, T.; Inanaga, J.; Yamaguchi, M. Tetrahedron Lett. 1986, 27,
5237 (in a racemic form).
(17) (a) Lowe, G. Chem. Commun. 1965, 411. (b) Brewster, J. H.
Top. Stereochem. 1967, 2, 1.
1
974, 107, 48.
15) (a) Krapcho, A. P.; Lovey, A. J. Tetrahedron Lett. 1973, 14, 957.
b) Krapcho, A. P.; Jahngen, Jr., E. G. E.; Lovey, A. J. Tetrahedron
Lett. 1974, 15, 1091.
(
(
5766 J. Org. Chem., Vol. 70, No. 14, 2005

Experimental Section
NMR (CDCl
1.9, 51.3, 52.5, 52.6, 87.4, 93.1, 169.4, 169.5, 204.0. Anal. Calcd
for C17 : C, 68.89; H, 9.52. Found: C, 68.79; H, 9.27.
meso- and dl-Dimethyl 2-Bis(2,3-dodecadienyl)propane-
3
): δ 14.1, 22.7, 28.1, 28.9, 29.1, 29.2, 29.3, 29.5,
3
Palladium-Catalyzed Asymmetric Synthesis of Allenes.
The reactions were conducted according to a reported procedure.
28 4
H O
2a
The reaction conditions and the results are described in Tables
and 2. A typical procedure is given for the reaction of entry 1
(29 mg, 50 µmol), (R)-binap
1
1
,3-dioate (meso- and dl-6). H NMR (CDCl
t, J ) 7.1 Hz, 6H), 1.26-1.39 (m, 24H), 1.93-1.98 (m, 4H), 2.63-
.65 (m, 4H), 3.71 (s, 6H), 4.86-4.92 (m, 2H), 5.03-5.08 (m, 2H).
3
): δ 0.88 (apparent
1
in Table 1: A mixture of Pd(dba)
2
2
2a
(
34 mg, 55 µmol), and (Z)-3-bromo-1,3-dodecadiene (2, 123 mg,
.502 mmol) was dissolved in THF (5 mL), and the solution was
(COOMe) (5, 80.0 mg, 0.605 mmol)
13
1
3
C{ H} NMR (CDCl ): δ 14.1, 22.7, 28.8, 28.9, 29.16, 29.17,
0
2
5
2
9.26, 29.28, 29.31, 29.4, 31.9, 32.48, 32.49, 52.33, 52.36, 52.40,
8.0, 58.1, 84.6, 84.7, 91.01, 91.03, 171.094, 171.096, 171.100,
added to a mixture of CH
2
2
and NaH (15 mg, 0.62 mmol) in THF (2 mL) by cannula transfer
under nitrogen. The mixture was stirred at 20 °C for 24 h and
then filtered through a short pad of silica gel to remove
precipitated inorganic salts. The silica gel pad was washed with
05.76, 205.81. Anal. Calcd for C29
48 4
H O : C, 75.61; H, 10.50.
Found: C, 75.36; H, 10.62.
Acknowledgment. This work was supported by a
Grant-in-Aid for Scientific Research (the Ministry of
Education, Japan), and the Kurata Foundation (to
M.O.).
small amount of Et
was evaporated to dryness under reduced pressure. The yellow
residue was chromatographed on silica gel (hexane/Et O ) 3/1)
to give the monoallene 3 (71.4 mg, 48% yield) and the bisallene
(as a mixture of meso- and dl-isomers. 102 mg, 44%). The
2
O three times, and the combined solution
2
6
characterization data of 3 and 6 are listed below. The allenes
Supporting Information Available: Experimental de-
9
-11 were characterized by comparison of their spectroscopic
1
13
tails for preparation of 2, H and C NMR spectra of 1,1-
2
a
data with those reported previously.
1
dibromo-1-decene, 2-4, and 6, and H NMR spectra for the
1
Dimethyl 2-(2,3-Dodecadienyl)propane-1,3-dioate (3). H
reaction products which were reported previously (1, 9-11).
This material is available free of charge via the Internet at
http://pubs.acs.org.
NMR (CDCl
.34-1.41 (m, 2H), 1.93 (dd, J ) 3.1 and 6.7 Hz, 1H), 1.96 (dd,
J ) 3.1 and 6.9 Hz, 1H), 2.56-2.60 (m, 2H), 3.51 (t, J ) 7.6 Hz,
3
): δ 0.88 (t, J ) 7.1 Hz, 3H), 1.26-1.33 (m, 10H),
1
H), 3.739 (s, 3H), 3.741 (s, 3H), 5.08-5.17 (m, 2H). 13C{ H}
1
JO050684Z
1
J. Org. Chem, Vol. 70, No. 14, 2005 5767